THE  PREPARATION  OF  ACID-FAST 

CARAMELS 


HY 

nONAJLD  FYFE  BOWEY 


THESIS 


FOK  THK 


DEGREE  OF  BACHELOR  OF  SCIENCE 


IN 

('BEMISTRY 


CUJLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1922 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/preparationofaciOObowe 


I92Z 

_BS7 


UNIVERSITY  OF  ILLINOIS 


May  34 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

.4. . . FyT®. . . .?  p.  w®.  y 

j 

ENTITLED . Acid-^^  


IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 


DEGREE  OF BaP.]Tel.QX...Qf....S.Gi.ano.0....in...CheM.s.try. 


Ya  l»JOr<sl  Yt/  H.'iaviu  aF^KT  HHT  TA^  Ot  U Slat 


%*4*b  ■:./'  ' 'ifjte&rt  -,  ■■'  * 

61?'  _ 'i-  ^ . . » _ _ M . , ^ ^ 1 'k-v. 


- •»4H«  r1«<*«**-** 


HHT  ac^  8TVl.-lU,HJ*t'K)^>l  .^HT  1<>'F  H/ M <^iav  OHU.fT'^JTIJl  SA  3M  Yd  L 

^ f. 

v'iS'Vvi  ' 


r ^ . 


;,j 


-i4..W«-*»»..-<M-.  Ik,..*  * ••('.•■MMIU<M'*l*-*'*»»*^r'  **•"•  ->  f»w.r»"Mt»-f  -> 


>»«rf«<f>  -♦-•4 


* ^ 

. lAk.  •t*l#tl.  M.llf*  I < ' • U ' 14 

•i.  ^ 

- . v‘ ImT.  h«  » r/MM  t ■«,)  aAYFf 


ttoLlwurtnyi-T 


M: 


Mi 


rfi 


TABLE  OF  CONTENTS 

Page 

ACKNOMiEDGIiENT 

I.  INTRODUCTION  1 

II.  HISTORICAL  3 

III.  EXPERIMENTAL  7 

IV,  AN  INVESTIGATION  OF  THE 

PURIFIED  CARAMELS.  19 

V.  CONCLUSIONS  33 

VI.  BIBLIOGRAPHY  33 


ACKN0?,'LEDG11ENT 
The  writer  wishes  to  express 
his  sincere  appreciation  for  the 
inspiration  and  helpful  suggestions 
from  Dr.  George  D.  Beal,  under  whose 
supervision  this  investigation  was 
carried  out. 


- 1 - 
I 

INTRODUCTION 

Caramel  is,  as  the  name  indicates,  hurned  or  carbonized 
sugar,  used  primarily  in  the  food  industries  whenever  a rich  brown 
color  is  required,  and  when  made  by  the  heating  of  cane  sugar 
without  chemical  reagents,  has  a secondary  value  as  a flavoring 
agent  in  confectionery,  baker's  goods,  etcetera.  Convenience  of 
preparation  and  the  fact  that  caramel  is  a representative  of  the 
harness  class  of  vegetable  colors,  combine  to  lend  popularity  to 
this  substance. 

The  investigation  of  carauTiels  has  attracted  the  sporadic 
interest  of  many  chemists  since  the  beginning  of  the  nineteenth 
century.  There  is  perhaps  no  subject  in  food  chemistry  that  has 
been  given  such  w'ork  and  throught  in  all  the  leading  countries 
and  has  yielded  such  .fruitless  returns  as  the  subject  of  caramiels. 

The  experiments  carried  on  by  these  earlier  chemists,  however, 
have  been  along  a purely  scientific  and  theoretical  basis.  They 
were  merely  interested  in  the  chemistry  of  caramels.  The  first 
half  of  the  nineteenth  century  was  spent  largely  on  the  analytical 
side  of  the  subject  and  finally  gave  way  to  the  mors  important 
investigation  of  the  synthesis  of  caramels. 

The  purpose  of  this  paper  is  somewhat  different  from  most  of 
the  literature  found  on  this  subject.  The  main  problem  deals  with 
the  preparation  of  a caramel  that  will  satisfactorily  comply  with 
all  the  tests  and  specifications  required  by  up-to-date  users  and 

will  be  sufficiently  economical  in  preparation  to  compete  with 


- 3 - 

commercial  caraunels  on  the  market  today. 

In  discussing  the  literature  available  on  the  subject  we  will 
mention  orily  briefly  the  works  of  the  earlier  chemists.  The  his- 
tory of  the  manufacture  of  caramels  will  be  disucssed  more  thor- 
oughly, the  uses  of  the  colors  and  finally  why  an  acid-fast  caramel 
has  been  demanded  for  commercial  consumption. 

The  second  part  of  the  paper  takes  up  the  preparation  of  an 
acid-fast  caramel  by  the  catalytic  distillation  of  commercial 
glucose  and  its  purification.  The  paper  is  concluded  with  an 
investigation  of  the  purified  caramel. 


r, 


7m  * 


‘i'  \ ^ yV;-! " 


.'1 1 ^ -' 

iv«.  > ' '■  k ! ' 


'^V 


J#-* 

■6'i 


aWBE..  . jM  ' 

*;  ? ■-'■  V :■**■  ■'  ■"  V;  'V.v  f . ■>  , ^ ^ 


fii  V ' 4^  '■  ''■'V'*-- '"' ' ' ‘ ^ '■  ■ ‘ '&."■'  '■*  ' 


m^' 


i;. 


, • - , T ••  I ' ' 'ii  V-  Tajre  jAr.^  ' 

hl,^zi'c  ^(!W  viLwM  y-M  /ttgyp:  ^m>>WfWy, 

1’  , , t ' ys^  ’''  ■ i- 


‘ *''  ■'  "Iff'  '■  '’'  ■ i"  ' ' ' “'-i 


'tii 


^ . tM  * • ■.  - V .'  » '•!  ’di,  . fSLr.-  : tJiffl 


111  M"  "W  '1.^  ■ ' ' 'm'lff 

- H?>  y. '\»  ;v  uaKIHI  ' ■.  .■'j,AJ»  — ■ w *> Ji 


"^1’' 


, ’‘^  ' y.:  “ 


1 

1 

< 


. ^ »'y 

‘ ry 


Ml 


,3. 


K.’'- 


i 


•I  ^ 


- i 


t 


^ tii 


-1  ^ 


- 3 - 

II 

HISTORICAL  FACTS. 

Caramel  is  regarded  as  an  intermediary  compound  formed  in  the 

dry  distillation  of  sugars.  It  may  be  obtained  from  the  various 

produce 

sugars  of  commerce  by  heating  them  to  the  temperature  necessary  to/ 
the  greatest  quantity  of  soluble  coloring-matter.  Different  temp- 
eratures are  required  for  the  carmeilization  of  different  sugars 
and  the  compounds  obtained  from  these  sugars  differ  a great  deal 
in  physical  and  chemical  properties.  (it  was  also  noticed  during 
the  course  of  the  experimental  work  that  these  same  properties 
were  changed  considerably  by  the  use  of  different  methods  for  the 
purification  of  the  caramel.) 

The  first  mention  of  this  subject  is  in  an  original  article 

(1) 

by  Peligot  . He  mentions  that  caramel  was  used  as  a coloring 

and  a therapeutic  agent  at  this  early  time  and  gave  it  an  empirical 

(3) 

form\ila  of  C4aH3  60is*  Volckel  working  a few  years  later  was  able 
to  throw  a little  additional  light  on  the  subject  but  came  to  an 
entirely  different  conclusion  regarding  the  structure  of  the  com- 
pound. He  assigns  to  caramel  the  emoirical  formula  C^gHgOg, 

(3) 

In  1858,  five  years  later,  Gelis  published  an  article  worth  con- 
sidering. He  made  three  distinctions  in  the  compounds  in  caramel, 
namely;  carmelene,  caramel in,  and  caramel ane.  These  showed 
differences  in  solubility  which  resulted  probably  from  increased 
molecular  weights.  He  gave  his  compound  the  formula  CigHie09* 

Gelis  was  the  first  man  to  notice  the  ■dissimilarity  between  the 
physical  and  chemical  properties  of  caramel  formed  from  glucose 


and  from  sucrose. 


- 4 - 


(4) 

In  the  dry  distillation  of  sugars  Trillat  shov;ed  that  there 

were  other  products  simultaneously  evolved,  such  as  formaldehyde, 

henzaldehyde , acetic  acid,  acetone,  phenolic  compounds,  etc.  The 

(5) 

latest  paper  on  the  chemistry  of  caramels  by  Cunningham  and  Doree 
covers  a large  field  ori  the  derivatives  and  reactions  of  this 
compound. 

The  theoritical  and  structural  investigations  of  caramels, 

however,  do  not  bear  as  directly  on  the  problem  of  this  paper  as 

do  the  investigations  on  the  preparation  and  manufacture  of  cara- 

(6) 

mels.  In  ISIO,  J.  J.  Kazewinkel  published  a method  for  the  manu- 
facture of  caramels  by  heating  molasses  with  15'^  of  water  at  135®C. 
for  5-10  hours.  He  states  in  his  paper  that  a higher  temperature 
shortens  the  time  of  caramel Izat ion  but  necessitates  mors  careful 
control.  He  also  advises  that  an  acid  caramel  should  be  neutral! zee 
before  using.  It  is  evident  from  the  time  necessary  to  prepare 
the  sugar  color  from  molasses  that  this  procedure  could  not  be 

satisfactorily  used  in  the  commercial  preparation  of  this  compound. 

(7) 

A few  years  later  A.  Herzfeld  prepared  a caramel  by  heating 
an  80^  invert  sugar  syrup  in  an  oil  bath.  He  found  that  the 
period  of  caramel izat ion  could  be  greatly  reduced  by  the  addition 
of  ammonia  from  time  to  time,  although  he  v/as  not  certain  just 
what  the  effect  of  this  catalyst  had  upon  the  reaction.  The  temp- 
erature was  raised  quickly  to  170®-80°C.  and  the  carai^isl  so  made 
complied  with  all  the  specifications  required  at  that  time.  One 


- 5 - 

great  advantage  of  this  compound  was  the  lack  of  the  bitter  taste. 
The  discovery  of  the  catalysing  action  of  ammonia  in  the  caramel- 
ization  of  sugars  was  a long  stride  forward  in  the  commercial 
manufacture  of  sugar  colors. 

(e) 

Another  acfirance  was  made  in  caramel  manufacture  when  L.  Eriant 
in  1913  stated  that  a desirable  compound  to  be  used  in  the  coloring 
of  beers  should  not  suffer  any  change  in  tint  when  treated  v;lth  a 
0.5^  solution  of  tartaric  acid.  He  prepared  his  caramel  by  heating 
glucose  with  the  addition  of  ammonia  and  its  salts.  This  is  the 
first  nublishwil  record  v/e  have  of  an  acid  test  for  caramels,  Erste 

(9) 

Wiener  Export  in  1919,  published  an  article  on  the  preparation  of 
caramels  from  sugars  in  the  presence  of  0,03-0,1^  of  its  weight  of 
acid,  a temperature  of  150  degrees  C.  being  employed.  He  does  not 
state  which  acid  was  used  but  it  is  supposed  that  one  of  the  more 
coi^on  Inorganic  acids  as  hydrocliloric,  nitric,  or  phosphoric  was 
employed.  The  presence  of  this  small  amount  of  acid  was  sufficient 
to  greatly  accelerate  the  reaction  with  the  formation  of  a very 
satisfactory  caramel. 

A few  papers  have  been  published  within  the  last  two  years  on 
the  manufacture  of  caramels  but  they  discuss  only  ordinary  methods 
of  preparation.  The  market  for  commercial  caramels  has  increased 
gradually  during  the  past  decade,  especially  since  the  passing  of 
the  Volstead  Act.  Although  this  compound  was  used  to  some  extent 
in  the  coloring  of  beers,  wines,  and  whiskeys,  its  principle  use 
at  the  present  time  is  in  the  soft  drink  industry.  The  bakers 


- 6 - 

and  candy  manufacturers  have  also  found  it  essential  as  a coloring 
agent . 

^Vith  this  marked  increase  in  the  caramel  industry, competition 
among  the  manufacturers  became  fairly  keen.  An  eastern  concern 
succeeded  in  manufacturing  by  a secret  process  a caramel  that  they 
advertised  as  being  acid-fast.  They  capitalized  this  test  until 
the  majority  of  caramel  users  in  the  country  would  accept  only  an 
acid-fast  caramel.  The  test  they  specify  is  as  follows:  Sixty 

grains  of  the  concentrated  caramel  are  dissolved  in  350  cc.  of  hot 
water.  If  one-half  of  this  volume  on  boiling  with  1 drahra  of  com>- 
mercial  hydrochloric  acid  v/ill  remain  clear  for  30  minutes  with  no 
visible  loss  in  tinctorial  strength,  it  is  said  to  be  acid-fast. 
Caramels  manufactured  by  ordinary  processes  will  not  stand  this 
test. 

It  has  been  proven  conclusively  by  investigators  that  ordinary 
sugar  colors  will  make  a very  satisfactory  coloring  agent  for  soft 
drinks,  bakers  supplies,  and  candies,  but  the  acid-fast  caramel 
has  been  advertised  to  such  an  extent  that  it  has  practically  be- 
come the  standard  of  the  industry.  The  preparation  of  a compound 
that  will  satisfy  this  test  is  explained  in  detail  in  the  experi- 
mental part  of  this  paper. 


- 7 - 
III 

EXPERILIENTAL  PART 

In  the  commercial  manufacture  of  caramels  the  glucose  is 

a 

heated  in  large  cast  iron  kettles  hy./coal  fire.  It  is  very  evident 
that  under  these  more  or  less  crude  conditions  a constant  temijer- 
ature  is  hard  to  maintain.  Rather  than  adopt  a similar  method 
in  the  laboratory  for  the  preparation  of  this  compound  it  was 
deemed  advisable  to  use  apparatus  which  would  allow  a much  closer 
control  of  the  caramel iz at ion  process.  The  apparatus  used  con- 
sisted of  a one-liter  Pyrex  flask  supported  in  a bath  of  cotton- 
seed oil.  The  oil  bath  fitas  kept  at  a constant  temperature  within 
the  range  of  a few  degrees,  and  served  as  a very  convenient  means 
of  distributing  heat. 

Pure  sucrose  was  tried  at  first,  but  it  was  found  to  be  an 
expensive  proposition.  Commercial  glucose  was  next  obtained  and 
was  analysed  optically  for  its  purity.  It  contained  18.68*^  water 
and  85.65'^  dextrose.  The  apparent  percentage  of  the  dextrose  was 
somewhat  high  due  to  impurities  that  were  not  removed  from  the 
sugar  solution.  Several  preliminary  batches  were  run  to  establish 
some  definite  method  of  procedure  which  would  give  the  desired 
results.  A very  satisfactory  method  of  cooking  is  as  follows: 

100  grams  of  glucose  are  melted  in  35  cc.  of  water.  The  empty 
pyrex  flask  ts  lowered  into  the  oil  bath  and  the  bath  heated  to 
the  temperature  desired.  The  melted  glucose  is  then  quickly 
poured  into  the  flask  and  the  time  noted,  a constant  temperature 


- 8 - 

bsing  held  throughout  the  entire  operation.  At  the  finish  of 
caramel ization  500  cc.  of  distilled  water  is  added  and  the  mixture 
allowed  to  stand  for  half  an  hour  to  dissolve  the  hardened  caramel. 
The  solution  is  then  filtered  through  weighed  Gooch  crucibles  to 
remove  the  char  and  other  insoluble  matter.  Char  sticking  to  the 
inside  of  the  flask  is  removed  by  warming  with  a 10^  solution  of 
sodium  carbonate. 

The  caramels  prepared  by  the  above  method  were  tested  for: 
acid-fastness,  tinctorial  strength,  and  percent  of  char,  the  three 
main  tests  on  which  a caramel  is  based.  The  acid  test  employed 
in  these  experiments  was  not  exactly  the  same  as  explained  in  the 
introduction  of  this  paper.  The  test  was  carried  out  by  diluting 
25  oc.  of  the  filtered  caramel  solution  with  50  cc.  of  distilled 
water,  adding  5 cc.  of  6 N.  hydrochloric  acid  and  boiling  the 
mixture  in  a small  beaker.  This  test  gave  comparative  results 
which  were  entirely  satisfactory.  Ordinary  caramels  broke  down  on 
10  to  15  minutes  boiling  with  this  concentration  of  acid  but  the 
acid-fast  compounds  remained  perfectly  clear  on  prolonged  boiling. 
The  formation  of  the  murky  solution  and  the  dark  brown  precipitate 
on  boiling  the  ordinary  sugar  colors  with  the  acid  is  probably  due 
to  the  hydrolyzing  action  on  the  unchanged  sugar.  If  this  state- 
ment were  true  it  is  obvious  that  an  acid-fast  caramel  could  be 
pfepared  by  converting  all  the  glucose  into  pure  caramel. 

The  caramel  was  tested  for  tinctorial  strength  by  diluting 
5 cc.  of  the  filtered  compound  in  a 100  cc.  measuring  flask.  This 
diluted  solution  was  then  tested  in  a standard  colorimeter  for  tint 


- 9 - 

Th3  tinctorial  numbers  used  in  the  follovdng  tables  can  only  be 
used  for  comparative  purposes,  the  higher  numbers  denoting  a higher 
tint. 

The  first  experiment  consisted  of  determining  which  temperature 
and  time  of  cooking  would  yield  the  best  caramel.  This  was  per- 
formed by  cooking  a series  of  batches  keeping  an  accurate  record 
of  the  time  of  the  heating  with  the  temperature  constant,  and  test- 
ing the  resulting  caramel  for  acid-fastness,  tinctoria.!  strength, 
and  percent  of  char.  The  weight  of  char  was  not  obtained  accurately 
on  the  analytical  balance  because  these  figures  were  only  needed 
as  a means  of  comparison.  In  the  first  series  of  batches  100  grams 
of  glucose  were  used  in  each  batch  without  the  addition  of  a 
catalyst. 


Time 

Temperature 

®c. 

^ of  Char 

Tinctor- 
ial no. 

Acid 

Test 

35 

min. 

310 

3.68fo 

23 

8 

min. 

30 

n 

210 

3.0lfo 

36 

10 

It 

35 

It 

310 

3. 34^0 

35 

10 

II 

40 

ti 

310 

3.39fo 

34 

10 

n 

45 

ti 

210 

2.53fo 

33 

10 

n 

50 

It 

210 

39 

10 

N 

65 

II 

310 

4.  OOfo 

36 

17 

II 

60 

It 

310 

6.  45fo 

33 

15 

n 

65 

It 

310 

5.18f. 

36 

15 

II 

70 

n 

310 

7,84fo 

40 

18 

II 

- 10  - 


Time 

Temperature 

®C. 

^ of  Char 

Tinctor- 
ial no. 

Acid  Test 

35 

min. 

320 

3.00fo 

25 

13 

min 

30 

n 

330 

6.67fo 

36 

15 

It 

35 

n 

330 

5.59/0 

38 

15 

It 

40 

n 

330 

3.07/ 

26 

13 

II 

45 

tt 

330 

4.78/ 

31 

16 

Tl 

50 

n 

330 

7.43/ 

35 

16 

IT 

55 

n 

330 

6.61/ 

33 

15 

It 

60 

n 

330 

4.  60/ 

55 

15 

Tt 

65 

n 

330 

7.18/ 

38 

16 

It 

70 

Tt 

330 

8.30/ 

43 

17 

II 

35 

Tt 

330 

3.15/ 

36 

13 

It 

30 

IT 

330 

3.36/ 

33 

13 

IT 

35 

n 

330 

5.19/ 

36 

15 

It 

40 

Tt 

330 

4.95/ 

3T 

15 

n 

45 

n 

330 

6.31/ 

36 

15 

IT 

50 

11 

330 

7.55/ 

38 

16 

TT 

55 

TT 

330 

7.85/ 

41 

18 

IT 

60 

TT 

330 

6.19/ 

38 

17 

TT 

65 

IT 

330 

5.50/ 

36' 

15 

TT 

70 

n 

330 

8,55/ 

43 

16 

TT 

- 11 


It  was  perfectly  apparent  from  the  above  .tests  that  an 
acid-fast  caramel  could  not  be  prepared  by  this  simply  dry  distilla- 
tion of  the  glucose.  Not  only  did  the  resulting  caramel  break  dovm 
on  boiling  with  the  acid  but  the  tinctorial  strength  was  far  too 
low  for  the  length  of  time  required  in  the  cooking.  It  was  also 
noted  that  the  caramels  containing  a higher  percent  of  char  gave  a 
higher  tinctorial  number  and  remained  clear  longer  in  the  acid. 

Previous  investigators  on  the  preparations  of  caramels  found 
that  by  the  addition  of  a fairly  dilute  solution  of  sodium  carbon- 
ate during  the  caramel izat ion  process  the  color  strength  would  be 
greatly  Increased.  Four  batches  were  prepared  by  adding  100  cc. 
of  a 10'^  solution  of  sodium  carbonate  at  the  start,  the  rest  of 
the  process  remaining  the  same. 


Time 

Teinperature 

°C. 

^ of  Char 

Tinctor- 
ial no. 

Acid  Test 

30 

rain. 

310 

3.58fo 

31' 

10  min. 

40 

n 

310 

4.  63fo 

35 

13  " 

50 

n 

310 

6,  95“^ 

45 

15  " 

60 

tt 

210 

8,30fo 

48 

15  ” 

The  tinctorial  strength  was  the  only  test  benefited  by  this 
method  so  it  was  discarded.  Other  test  batches  were  cooked  by 
adding  larger  and  smaller  amounts  of  sodium  carbonate,  by  adding 
it  at  the  end  of  the  cooking  instead  of  at  the  first  and  by  adding 
it  in  aliquot  portions  throughout  the  caraxasl  izat  ion  prdcess,  but 


V • 


t 


L 


V 


4 


M 


X 


V 


i ■■ 

'■•.r.C’^£'  ’ 

vCX  r.  ■: 
- ^ 

■6  a'' 

A.,, 

■;  ■ V c;  otj 

, ■ 
■1  i 

! n'i^' 

u: 


t r 


- 13 


all  of  these  experiments  gave  practically  the  same  results.  Erste 
Wiener  Export  (loo.  cit. ) stated  that  a satisfactory  caramel  could 
be  prepared  by  the  addition  of  a very  small  amount  of  acid.  Four 
test  batches  were  prepared  by  the  addition  of  5 cc.  of  dilute 
hydrochloric  acid  (one  p?-rt  6 N.  hydrochloric  acid  to  sixteen 
parts  of  water)  plus  the  10  cc.  of  sodium  carbonate  solution 
added  at  the  beginning  of  the  process. 


Time 

Temperature 

®C. 

^ of  Char 

Tinctor-r 
ial  no. 

Acid 

Test 

30 

min. 

310 

3.68f« 

38  . 

13 

min. 

40 

n 

310 

3,98f. 

39 

13 

It 

50 

It 

310 

5.  48*^ 

38 

13 

n 

60 

I! 

310 

5.65fo 

43 

15 

ft 

The  use  of  hydrochloric  acid  seemed  to  cut  down  the  percent- 
age of  char  but  the  tinctorial  strength  and  the  acid  test  remained 
about  the  same.  Sulfuric,  phosphoric,  and  nitric  acids  were  tried 
with  no  improvement  in  the  resulting  caramel.  It  was  very  evident 
that  these  reagents  were  out  of  the  question  for  the  preparation 
of  an  acid  fast  color. 

During  the  cooking  of  the  test  batches  the  caramel  just  at 

the  cracking  point  rose  rapidly  up  to  the  neck  of  the  flask  and 
frothed  considerably.  It  seemed  that  if  a method  could  be  devised 
to  keep  the  caramel  from  frothing  during  the  cararnelization  process 
the  time  of  cooking  would  be  greatly  reduced.  It  was  impossible 
to  use  a stirring  device  that  would  scrape  the  sides  of  the  flask. 


- 13  - 

If  the  addition  of  a volatile  chemical  would  keep  the  sugar  in 
constant  motion  and  yet  not  affect  the  composition  of  the  caramel, 
the  method  of  cooking  would  be  greatly  improved.  Ammonium  Chloride 
was  first  tried.  A series  of  batches  were  burned  with  the  addition 
of  5 cc.  of  a 10*^  solution  of  ammonium  chloride  at  the  beginning 
of  the  batch. 


Time 

Temperature 

°C. 

^0  of  Char 

Tinctor- 
ial no! 

Acid 

Test 

15 

min. 

200 

8.  63fo 

121 

30 

min. 

16 

n 

200 

8, 95 fo 

126 

30 

17 

ti 

200 

9,54fo 

127 

30 

n 

18 

n 

200 

ll,65fo 

135 

30 

1? 

19 

n 

200 

13.  48fo 

133 

30 

ij 

20 

n 

200 

15.63fo 

133 

30 

n 

The  results  obtained  by  the  use  of  the  salt  were  surprising. 
It  took  only  one-third  of  the  time  previously  required  for  the 
caramel ization  process,  it  did  not  froth,  it  gave  a much  higher 
tinctorial  number,  and  it  was  acid-fast.  Apparently  the  batch 
which  was  burned  in  18  minutes  gave  the  best  results.  Using  this 
time  of  heating  and  a temperature  of  300°C.  several  batches  were 
prepared  with  different  amounts  of  the  salt.  The  left  hand  coluinn 
represents  the  amount  of  10^  solution  of  ammonium  chloride  used. 


- 14  - 


Amount 

Temperature 

°c. 

^ of  Char 

Tinctor- 
ial no. 

Acid 

Test 

10  cc. 

300 

35.63fo 

143 

30 

min. 

9 " 

300 

34.03fo 

140 

30 

n 

8 " 

300 

19.35f» 

141 

30 

n 

y »i 

300 

16.  4Bfo 

138 

30 

n 

6 " 

300 

13.76fo 

135 

30 

n 

5 " 

300 

13.89fc 

138 

30 

tt 

4 

■ 300 

9.05fo 

131 

35 

n 

3 " 

300 

3.35fo 

96 

15 

n 

It  is  obvious  from  these  results  obtained  that  5 cc.  of  the 
salt  solution  gave  the  best  results.  This  amount  of  ammonium 
chloride  was  used  in  combination  with  dilute  solutions  of  hydro- 
chloric, sulfuric,  and  phosphoric  acids,  but  jjhe  only  difference 
noted  was  a slight  increase  in  the  tinctorial  number.  Although 
this  method  produces  a satisfactory  acid-fast  caramel,  the  cost 
of  the  aiamonium  chloride  is  a little  too  high  to  be  used  in  the 
economical  preparation  of  She  compound. 

Commercial  an^aonium  sulfate,  which  is  much  cheaper  than  the 
chloride  was  next  tried.  A series  of  batches  were  cooked  by 
the  addition  of  5 cc.  of  a 10^  solution  of  ammonium  sulfate  at 
the  beginning  of  the  run.  The  time  of  heating  was  varied  but 
the  temperature  was  kept  constant. 


- 15 


Time 

Temperature 

°C. 

^ of  Char 

Tinctor- 
ial no. 

Acid  Test 

15  min. 

300 

6.33fo 

135 

35  min. 

16  " 

300 

7,86f. 

138 

35  ” 

17  " 

300 

131 

30  ” 

18  " 

300 

6.64f^ 

143 

30  " 

18  " 

SCO 

10.83^; 

144 

30  ” 

30  " 

300 

15.  edfo 

149 

30  " 

Again  heating  for  a period  of  18  minutes  seemed  to  give  the 

best  results, 

. By  varying 

the 

amounts  of 

the  salt  solu 

tion  and 

heating  at  a 

temperature  of  300®C.  for  18 

minutes,  the 

quantity 

of  salt 

necessary  to  give 

the 

best  results  was  obtains 

d. 

Amount 

Temperature 

®C. 

^ of  Char 

Tinctor- 
ial no. 

Acid  Test 

10  cc. 

300 

21,  61  fo 

153 

30  min. 

9 " 

300 

33  . 45^ 

151 

30  ” 

8 " 

300 

19.83fo 

146 

30  " 

7 ” 

300 

21,07fo 

143 

30  ” 

6 " 

300 

l5.93fo 

138 

30  " 

5 ” 

300 

13.48f^ 

140 

30  " 

4 " 

300 

6,52fo 

136 

30  ” 

3 ” 

300 

4.8lfo 

116 

30  ” 

In  this 

series  of  experiments 

the  10  cc. 

of  salt  solution  seemed 

to  give 

the 

'oest  caramel. 

The  amount  of 

salt  was  cut 

dov\,m  con- 

siderably  by 

the  addition 

of 

a small  amount  of  acid. 

The  above^ 

- 16 


experiment  was  repeated  v;ith  the  addition  of  3 cc.  of  dilute  hydro- 
chloric acid  (page  10)  at  the  beginning  of  every  run. 


Amount 

Temperature 

®C. 

fo  of  Char 

Tinctorial 

number 

Acid 

Test 

10  cc. 

300 

16.05^ 

168 

30  : 

min. 

9 " 

300 

17.95f. 

161 

30 

n 

8 " 

300 

15.3lfo 

158 

30 

n 

7 " 

300 

10.65fo 

145 

30 

n 

6 " 

300 

13.77f. 

.151 

30 

n 

5 " 

300 

lO.OOffi 

149 

30 

4 « 

300 

8.78fo 

145 

30 

n 

3 « 

300 

e.3Zfo 

130 

35 

n 

The  presence  of  the  acid  reduces  the  amount  of  salt  required 
to  about  one-half,  as  seen  clearly  by  the  last  two  experiments, 
the  quality  of  the  product  being  practically  the  same  in  both 
cases.  An  attempt  was  made  to  substitute  sulfuric  and  phosphoric 
acid  for  the  hydrochloric  but  a very  poor  product  resulted  from 
the  use  of  both  of  these  acids.  The  preparation  of  an  acid-fast 
caramel  can  best  be  effected  by  caramelizing  in  the  presence  of 
a small  amount  of  ammonium  sulfate  and  a weak  solution  of  hydro- 
chloric acid. 

There  is  present  in  ordinary  carai^iels  a small  amount  of  un- 
changed sugar.  The  methods  of  purification  used  to  remove  this 
sugar  are  enumerated  by  previous  investigators,  vho  purified  the 


- 17 


the  product  were;  precipitation  by  alcohol,  fermentation,  and 

(10) 

dialysis.  The  first  two  methods  were  considerably  harder  to  use 
than  the  last  method  and  were  not  employed  for  the  purification  of 
the  caramel. 

For  experimental  purposes  caramel  can  be  purified  very  readily 
by  dialysis  through  a collodion  membrane,.  The  membrane  ms 
prepared  by  rotating  the  collodion  solution  in  a 350  cc.  Erlenmeyer 
flask,  pouring  off  the  excess  collodion,  allov/ing  it  to  dry  over 
night,  and  drawing  out  the  bag  with  the  assistance  of  a fine  stream 
of  water.  The  bags  prepared  in  this  manner  were  water  tight  and 
were  sufficiently  strong. 

About  300  oc.  of  the  caramel  solution  was  poured  in  one  of  the 
bags  with  a small  capillary  tubs  fastened  in  the  constricted  end 
of  the  bag  and  then  supported  in  a large  beaker  containing  distilled 
water,  with  the  v/ater  and  the  solution  in  the  bag  at  the  same  level. 
The  caramel  solutions  were  allowed  to  dialyze  for  48  hours,  the 
water  being  changed  several  times  during  the  process.  The  caramel 
solutions  and  the  water  solutions  outside  the  bag  were  then  tested 
for  the  absence  or  presence  of  sugar,  formaldehyde,  and  acetic 
acid. 

In  the  dialysis  of  caramels  prepared  without  the  use  of  chem- 
icals the  unchanged  sugar,  formaldehyde,  and  acetic  acid  passed 
through  the  bag  very  rapidly  as  sho^vn  by  qualitative  tests  applied 
at  different  intervals  to  the  water  solution.  The  resulting  car- 
amel contained  none  of  the  above  mentioned  substances,  When  boil- 
6d_ vith  hydrochloric  acid  thg  solution  remained  clear  for  over  30 


- 18 


minutes  showing  that  the  purified  product  was  acid-fast. 

The  caramels  prepared  by  the  use  of  the  ammonium  salts  were 
next  dialyzed  for  a period  of  48  hours.  The  water  solution  at 
the  end  of  the  first  13  hours  gave  absolutely  no  tests  for  sugar, 
formaldehyde,  acetic  acid,  and  ammonium  salts.  At  the  end  of  the 
46  hours  the  water  solution  was  slightly  acid  to  litmus  and  gave 
evidence  of  a trace  of  the  ariimonium  salts.  The  caramel  solution 
was  acid-fast, both  before  and  after  dialysis.  It  is  evident  from- 
these  experiments  that  the  acid-fastness  of  a caramel  depends 
upon  the  absence  of  the  unchanged  sugar,  as  the  action  of  the 
dilute  hydrochloric  acid  on  the  sugar  causes  hydrolysis  with  the 
formation  of  a murky  solution. 


~ 19 


IV 

AH  IHVESTIGATIOH  OF  THE  PURIFIED  CARAMELS. 

One  of  the  most  interesting  studies  on  the  subject  of 
caramels  since  the  earliest  investigations  has  been  the  determin- 
ation of  a suitable  empirical  formula  for  the  compound.  Results 
have  differed  so  v/idely  on  this  value  that  it  seems  probable  that 
there  is  a different  compound  formed  with  each  different  method  of 
preparation  of  the  caramel.  To  reach  a satisfactory  proof  of  this 
statement  the  molecular  weights  of  oaramesl  prepared  by  two  differ- 
ent processes  were  determined. 

The  freezing  point  method  was  used  in  this  investigation  and 
although  it  was  extremely  hard  to  get  check  results,  seven  deter- 
minations wore  run  on  each  caramel  to  obtain  a satisfactory  aver- 
age. The  average  of  the  res’ults  obtained  check  fairly  close  with 

(11) 

the  value  given  by  Beal  and  Zoller  for  the  molecular  weight  of 
a glucose  caramel.  The  first  series  of  determinations  were  made 
on  the  purified  product  obtained  from  the  ordinary  distillation 
of  commercial  glucose. 

Glucose  caramel  — -503-509-513-514—506-509-511 

Average 509,8 

This  value  of  509.8  checks  reasonably  close  v/ith  the  value  of 
516,  as  obtained  by  Zoller,  and  seems  to  indicate  the  empirical 
formula  of  this  caramel  would  be  CgoHaoOis* 


- 30- 


Howevsr,  in  the  determination  of  the  molecular  weights  of 
the  caramels  prepared  by  the  use  of  the  aniinonium  salts  an  entirely 
different  value  ?;as  obtained,  A series  of  molecular  weight  de- 
terminations v/ere  made  eon  the  ammoniuirx  sulfate  caramel  and  the 
average  value  wasx. considerably  less  than  that  obtained  above. 


Glucose  Caramel 458 -470-466r5- 493 -489-495 -488 

Average -484.  8 


This  average  would  call  for  empirical  formula  of  CisHsoOib  which 
appears  entirely  possible.  Zoller  also  points  out  that  the  glu- 
cose caramel  might  possess  a polymeric  hexose  structure  as 
(C6Hi206)3*  The  action  of  the  ammonium  sulfate  on  the  oarameliza- 
tion  process  accelerates  the  dehydration  of  the  molecule  and 
if  this  formula  was  assumed  correct  the  action  of  the  salt  might 
be  illustrated  by  the  following  equation. 

(C ©Hi 303)3 ^ ( C 6^'^io^s ) 3 + 3 KsO 

The  formula  (CeH 1005)3  would  call  for  a molecular  weight  of  486, 
which  approximates  very  closely  the  value  obtained  experimentally. 
Hydrolysis  of  the  Benzoyl  Derivative.  The  benzoyl  derivative 
was  prepared  by  shaking  the  acidpfast  caramel  with  a slight  ex- 
cess of  benzoyl  chloride  in  the  presence  of  sodium  hydroxide. 

The  derivative  thus  prepared  had  a light  brown  color  and  appeared 
to  be  a mixture.  It  was  not  entirely  soluble  in  glacial  acetic 
acid,  much  less  in  other  comon  solvents,  so  that  a molecular  weight 
determination  could  not  be  made  by  the  freezing  point  method. 


- 31 


In  order  to  obtain  some  knowledge  of  the  number  of  benzoyl 
groups  which  had  been  substituted  for  the  hydrogen  of  the  hydroxyl 
groups,  the  derivative  was  hydrolyzed  and  the  percentage  of  benzoic 
acid  determined.  3 grams  of  the  purified  derivative  were  v/eighed 
accurately  into  a 500  cc.  flask.  Exactly  50  cc.  (measured  from  a 
pipette)  of  a standard  10*)?’  solution  of  sodium  hydroxide  were  then 
added  and  the  mixture  refluxed  for  thirty  minutes.  The  clear 
solution  was  then  poured  into  a liter  volumetric  flask,  made  up 
to  the  mark,  and  50  cc.  removed  for  titration.  The  excess  alkali 
7/as  titrated  with  0.5  N.  hydrochloric  acid,  using  a mixture  of 
methyl  red  and  methylene  blue  as  an  indicator.  The  amount  of 
benzoic  acid  was  then  very  readily  calculated. 

The  average  amount  of  benzoic  acid  calculated  from  a series 
of  titrations  was  4.98)^.  This  axiiount  is  very  low  and  it  shows 
clearly  that  the  number  of  benzoyl  groups  attached  in  the  derivative 
are  comparatively  few. 


Tt 


*■  • ’ ■;  ' . ■ ' ■ ^ : 


•-■Hr'*  -4  ' 


" ‘I’  ^.. 


, ,♦.*•  .y 


4*.  ■ i 

I.'  ^ r 


f 


V 


i 


7 


/ ;>■ 


*v 


- ■ 


-H 


< ; 7 


I >•  • \ ■ .f 


* / t j » ' 

r *y»  ^ 


\ 


i j<  : 


1 


I 


^ V. 


/ 


Tv, 


ki 


/ 

A 


‘W 


I -It 

r 


'• 


fr- “<  - • -V  ■vC*..'-  •*»*>*■“■ 


T-  r •*■ 


- 33 


V 

CONCLUSIONS 

(l)  A satisfactory  caramel  can  be  prepared  by  the 
caramelization  of  a commercial  glucose  in  the  presence  of 
a small  amount  of  armnonium  sulfate  and  hydrochloric  acid, 

(3)  The  amionium  sulfate  and  hydrochloric  acid  act 
purely  as  catalysts  and  probably  accelerate  the  dehydration 
of  the  molecule. 

(3)  Acid-fast  caramels  contain  no  unchanged  sugar  as 
illustrated  by  the  dialysis  of  the  caramels  through  a collod- 
ion rflembrane. 

(4)  Caramels  prepared  by  different  methods  have  different 
values  for  molecular  weights  and  consequently  must  have  vary- 
ing molecular  structures. 

(5)  The  number  of  hydroxyl  groups  in  the  caramel  molecule 
is  dependent  upon  the  completeness  of  the  dehydration  of  the 
molecule,  the  more  complete  the  dehydration,  the  fewer  the 
hydroxyl  groups,  as  sho'im  by  the  percentage  of  benzoic  acid 

in  the  benzoyl  derivatives. 


23 


VI 

BIBLIOGRAPHY 

(l^  Ann.  de  Chemique  et  Physique,  2nd  ser.  67-172-1838. 

(2)  Annalsn  der  Cherai.  Vol.  85-86-89-1853. 

(3)  .Ann.  de  Chemique  et  Physique,  Vol.  52-352-1858 

(4)  Bui.  de  la  Societe  Chemique  de  Paris,  90-681-1906. 

(5)  J.  Chem.  Society,  111-589-608-1917. 

(6)  Z.  Suikerind  Bijblad,  No.  40-497-524-1910. 

(7)  Deut.  Zuckerind,  35-617-618. 

(8)  J.  Inst.  Brewing,  Vol.  8-673-686-1913. 

'.(9) . Malzfabrik  House  and  Sobotka,  Dan.  24-843-1919. 

(10)  . Beal  and  Zoller,  Jour.  Amer.  Pharm.  Assoc.,  April,  1914, 

490. 

(11) '  Beal  and  Zoller,  Private  Communication. 


